Ointments, patches, or the like for transdermal and transmucosal administration, in addition to injections, oral preparations, and suppositories have conventionally been subjected to research and development as dosage forms of drugs such as physiological active substances. Transdermal and transmucosal administration has various advantages over the other administration methods, such as easiness in administration, maintenance of drug concentrations in blood, and avoidance of gastrointestinal adverse drug reactions. By transdermal and transmucosal administration, however, drugs are generally not absorbed well, and there are problems in absorption time and amount especially for drugs having a high molecular weight.
Various research and development efforts have been made on absorption-enhancing methods to increase drug absorption from the skin and mucosa. These methods include chemical enhancing methods using absorption-enhancing as well as physical enhancing methods using iontophoresis, phonophoresis, electrophoresis, or the like. Among these, in the case of iontophoresis, a drug is administered into a body via the skin or mucosa by applying voltage to the skin or mucosa to make an ionic drug migrate electrically.
Methods for energization applied for iontophoresis include direct current type energization, pulse type energization, and pulse depolarized type energization. Among these, pulse depolarized type energization has advantages such as that it is excellent in terms of drug permeability, as compared to the direct current type and pulse type energization methods, and that it causes only weak irritation on the skin and mucosa, even when applying a large electric current. The pulse depolarized type energization is described in, for example, Japanese Patent Laid-Open Publication No. 60-156475.
Since the pulse depolarized energization has the above-mentioned advantages, the method is quite useful for use in a device for iontophoresis. The present inventors faced a new problem, however, when attempting to provide a practical application of a device, in that it was difficult to design a small and portable device using this energization method. The problem is that the pulse depolarized energization consumes more electric power than the direct current type and pulse type energization methods. It is, thus, difficult to realize a reduction in device size and to obtain a portable device without solving this problem.
Therefore, it is an object of the present invention to provide a transdermal or transmucosal drug delivery device excellent in terms of drug permeability and skin irritability and capable of reducing electric power consumption.